I would really like to do my advanced editing in AE but when I try to export as a .avi, it comes out as a file with nothing on it. It will still have the filesize that it would originally have but nothing on it. When I try to play it, it is just a black with no sound. I wasted about 30 minutes exporting it and nothing was on it. It did work before, this isn't my first time using after effects. Every other time it came out just fine. Please help, I would really like this to work.

I don't think I have changed any of the settings and when that avi exporting window comes up, sound and video are checked. I'm not sure what could be the problem could be.

What codec are you rendering to? Perhaps render to another format, and then see if you could rerender that for your avi. If you have premiere or another compression program, you could load your rendered image sequence (or lossless QT:Animation) and compress in that.

Ah - that's your problem.. Don't use File/Export. Instead use the Render Queue (read up in help for more info than I can type...)

To render your movie, set your work area for the full amount you want to render. Hit ctrl-m to Make Movie (adds it to the render queue). Set your options and you should be good to go. Realize that AE can't do multipass compression, so as I mentioned before, you might be better off rendering to a lossless format (tga sequence with RLE enabled, QT:Anim) and then compressing it in another program.

Also, some formats require specific resolutions.. If you are still having problems, please mention your comp settings, render settings, and render format/codec.